IOA 2022

Alpha Angle More Useful Than Femoral Head-Neck Offset to Predict Intra-Articular Damage in Patients with FAI Undergoing Hip Arthroscopy

Jackob Shapira 1 Jade Owens 1 David Maldonado 1 Phillip Rosinsky 1 Hari Ankem 1 Bezalel Peskin 1 Ajay Lall 1,2 Benjamin Domb 1,2
1Orthopedics, American Hip Institute Research Foundation, USA
2Orthopedics, American Hip Institute, USA

Purpose:
To identify radiographic measurements and demographics that are predictive of intra-articular cartilage damage in patients with femoroacetabular impingement (FAI) undergoing hip arthroscopy. More specifically, to compare the predictive value of alpha angle and femoral head-neck offset in determining the preoperative likelihood and severity of intra-articular cartilage damage.

Methods:
Patients were included if they underwent primary hip arthroscopy between February 2008 and June 2020. A total of 13 variables were assessed in a bivariate comparison and analyzed in a multivariate logistic model. The Acetabular Labrum Articular Disruption (ALAD) and Outerbridge (OB) classifications were used to define acetabular cartilage defects. Those without damage or those with mild acetabular cartilage damage belonged to the ALAD/OB ≤ 2 group and those with severe acetabular cartilage damage belonged to the ALAD/OB ≥ 3 group.

Results:
The multivariate logistic regression selected age, sex, anterior center-edge angle (ACEA), and alpha angle. Every additional degree in the alpha angle was associated with a 6% increase in the odds of severe acetabular cartilage damage defined as ALAD/OB ≥ 3 (OR, 1.06 [95% CI, 0.12-8.11]). The multivariate analysis did not identify femoral head-neck offset as a predictor. The odds of severe acetabular cartilage damage were 3.73 times higher in males than females (OR, 3.73 [95% CI, 0.01-1705.96]). Higher age (per log 10 unit) was found to increase the likelihood of ALAD/OB ≥ 3 (OR, 1.04 [95% CI, 0.13-7.75]).

Conclusions:
In a multivariate analysis, factors identified as preoperative predictors of intra-articular cartilage damage in patients with FAI were age, sex, ACEA, and alpha angle. Femoral head-neck offset was not predictive, suggesting alpha angle may take precedence as a predictor of intra-articular cartilage damage. These findings may be helpful to the clinician’s efficient utilization and selection of radiographic predictors of intra-articular cartilage damage in patients with FAI undergoing hip arthroscopy.